L-Tryptophan is one of the essential amino acids constituting the bodies of animals, and is important as a medicine, nutrient, or as an additive for animal feed. Some L-tryptophan derivatives work as an antagonist against the metabolism of L-tryptophan and contain physiologically active substances that may be used to prepare pharmaceuticals that affect the central nervous system. These L-tryptophan and its derivatives can be produced by known methods of synthesis, biological process and many other methods. Known methods for producing L-tryptophan using microorganisms include: (1) direct fermentation using sugars to accumulate L-tryptophan in a culture; and (2) adding indole or anthranilic acid simultaneously with sugar to a culture, and permitting L-tryptophan to accumulate in the culture. L-Tryptophan can also be produced from indole and serine or from indole, pyruvic acid and ammonium ion by using a microorganism-produced tryptophanase (enzyme). This method of using tryptophanase has the advantage that by replacing the indole with other indole compounds, various corresponding L-tryptophan derivatives can be produced, and that hence, a reaction that best suits a particular purpose can be selected.
Many methods are known for producing L-tryptophan using tryptophanase. Japanese Patent Publication No. 46917/74 describes a method wherein L-tryptophan is produced from indole and serine or from indole, pyruvic acid and ammonium ion using a microorganism of genus Escherichia, genus Proteus, genus Pseudomonas, genus Aerobacter or genus Erwinia, and French Pat. No. 1,207,437, Japanese patent application (OPI) No. 39693/72 ("OPI" as used herein means an unexamined published Japanese patent application) and Japanese Patent Publication No. 1836/78 describe a method wherein L-tryptophan is produced from indole and serine using a microorganism of genus Escherichia, genus Claviceps, genus Neurospora, genus Saccharomyces, genus Bacillus, genus Achromobacter or genus Alcaligenes. Several methods are also known for producing L-tryptophan derivatives that correspond to various indole compounds: Japanese Patent Publication No. 46917/74 describes a process for producing 5-hydroxytryptophan using a microorganism of genus Proteus, genus Escherichia, genus Pseudomonas, genus Aerobacter or genus Erwinia; Japanese Patent Publication No. 1835/78 describes a method for producing 5-hydroxytryptophan using a microorganism of genus Achromobacter, genus Escherichia, genus Pseudomonas, genus Alcaligenes or genus Proteus; and Japanese Patent Publication Nos. 5479/76 and 8400/77 describe a method for producing 5-hydroxytryptophan and methoxytryptophan using a microorganism of genus Corynebacterium or genus Brevibacterium.
These methods that use microorganisms are advantageous over the method for producing L-tryptophan or its derivatives by chemical synthesis because they provide only L-form compounds that are optically active. They make possible production of large quantities of L-tryptophan or L-tryptophan derivatives from industrial materials such as indole compounds, serine, or pyruvic acid.